Skittish retail investors are coming back around to their favorite bet: artificial intelligence. According to Citadel Securities’ Scott Rubner, retail traders net bought $9.1 billion of US equities on the firm’s platform last week, largely concentrated in AI-tied stocks and exchange traded funds, even as overall trading activity remained below average. It was the largest week of net buying in 15, the firm’s head of equity and derivatives strategy wrote in a note.

Despite doubts about the durability of the AI boom weighing on chip stocks, retail bought $2.6 billion on net of semiconductors last week, logging the third-best week of the past year, Rubner said. That puts October on track to be the biggest month of net buying for chipmakers on the company’s platform. Individual traders also bought about $2.4 billion of AI infrastructure stocks.

Investors keep putting money into the AI trade, propelling the broader gauges higher, despite warnings about an AI bubble. Both the tech-heavy Nasdaq 100 and the S&P 500 set record highs last week.

Rubner correctly called this month’s return of retail investors to US stocks at the beginning of October after a sharp cooldown in September. He noted at the time that October offers a better entry point for investors to “reload” as earnings and corporate buybacks are set to return.

The increase in retail buying was generally driven by “stronger directional conviction rather than elevated volumes,” Rubner wrote. Retail investors bought 2.7% more than they sold last week, which is a 90th-percentile reading for weekly directional skew. Gross trading activity remained in the 42nd percentile of the past year.